The excitation of coherent electromagnetic radiation in plasma waveguides by relativistic electron beams

A theoretical analysis is presented of the interaction between a monoenergetic relativistic electron beam and a bounded plasma and the conditions for the generation of electromagnetic radiation in a single mode by such a system are derived. Two specific geometries are considered: (a) a metallic waveguide of radius R, completely filled with plasma which is penetrated by a beam of the same radius and (b) a plasma cylinder of radius r0, with a hollow beam flowing along it and filling a metallic waveguide of radius R>r0. The spectra and growth rates of the excited oscillations are established and the generation efficiencies calculated.